Telephone instrument



H. F. OBERGFELL 1,956,360

TELEPHONE INSTRUMENT April 24, 1934,

2 Sheets-Sheet 1 Filed May 11, 1931 22/? as a2 80 .30 our Alva HOLDfave-mm- I HErbETF UJJZZ April 24, 1934.

H. F. OBERGF'ELL TELEPHONE INSTRUMENT Filed May 11. 1931 2 Sheets-Sheet2 How s our I 3 HOLD,

lmfil'u-f Harsh EFT F D1211 Patented Apr. 24, 1934 issasto 1 UNITEDSTATES TELEPHONE INSTRUMENT Herbert F. Obergfell, River Forest; 111.,asaignor,

by mesne assignments, to Associated Laboratories, I nc., Chicago, 111.,a corporation of Delaware Electric Application May 11, 1931, Serial No.536,424-

io Claims.- (01. 173- 100).

The presentinvention relates in general to telephone instruments, butmore particularly to a new and improved substation. telephone instrumentwithwhich it is possible to communicate over two or more, differentkinds of telephone systems from the same instrument, such as, forexample, a private branch exchange and a central public exchangetelephone system.

Telephone instruments of the above type have been usually provided witha n ber of pushbuttons for performing the various switching. op- 1erations, one of the buttons being used for talking with a subscriberonone system, a second button for talking to a subscriber on anothersystem, and a third push-button when a connection is desired with onesubscriber while hold-- "ing the other subscriber. When a connection inany case was released, the operated push-buttons had to be manuallyrestored to normal or, as was the usual case, it was necessaryto note orcheck the operated or non-operated condition of the push-buttons when acall was to be made or answered.

It is an object of this invention to design a telephone instrunientwhicheliminates the use of the objectionable push-buttons and at the sametime provides animproved'means of giving the above and additionalservices in a telephone system,

In accordance with this so particular feature of the invention r des inpro ding a number of lever type keys together with means forautomatically restoring them to normal position when a telephoneconnection is terminated. One of the keys is operated when a mainexchange call is desired, another whenmore than one main exchangeconnection is to be made and it' is ,de-' sired to hold one connectionwhile another connection is being established, and a third key foranswering incoming main exchange calls.

i A feature of the invention resides-in the provision of'means wherebylocal calls may be madev ,or answered without the'necessity of operatingany of the keys.

An additional feature'is concerned with an interlocking arrangementbetween several of the keys so that only one at-a time can be operatedto perform certain circuit changes and prevent the mutilation ofexisting connections.

An additional feature of the invention resides in providing an auxiliarystand or sub-base for a standard telephone instrument which serves'as anenclosure and support for the keys so that they are convenientlyaccessible for operation.

The above objects and features and others not specifically pointed outwill be apparent from the auxiliary base 3 is, provided with anadditional detailed description which, together with the two sheetslofdrawings, constitutes a preferred embodiment of the invention.

In the drawings, Fig. l shows a perspective view of an ordinary cradletype of desk telephone supported on an auxiliary base containing anumberof lever type keys; Fig. 2 illustrates a top view of the lever keyarrangement detached from the sub-base of the telephone and showing thecontact spring combinations controlled by the lever keys; Fig. 3 is across-sectional side view along the line 3-3 looking in the direction ofthe arrows of Fig. '2, with. certain parts omitted for the sake ofclearness'; Fig. 4 is a rear view of Fig. 2 showing the lever keyarrangement; while Fig.5 is a schematic representation of the circuitarrangement involved in a telephone-substation of the invention..Referring now more particularly to Fig. 1, this shows a well-known orle-type telephone set 7 having a base or standa d 2 supporting a cradle,member 1, for the handset. The handset (not shown) normally restsbetween the posts of the I cradle member 1- and in this position itpresses down the hookswitch member 45 which controls the hookswitchsprings. A sub-base or auxiliary base 3 of the general shape indicatedserves as a support for the base 2 of the telephone. This base plate 4for enclosing the apparatus contained in the base, which may be coveredwith rubber or felt-so that polished surfaces will not be scratched inmoving the telephone. An impulse sender or calling device 18 is mountedon the front side of the base 2 and is used for extending telephoneconnections. An opening in the subhased?- is provided at the front ofthe telephone immediately below the calling device 18, and a number oflever'keys 10, 20, and 30 extend through this opening. These lever keysare with a number of extensions formed at right angles to andon one sideof the body of the bracket. The extensions 6 and '1 formed on each sideof the rear of thebracket serve as mounting plates for a number ofspring combinations and provide bearing means for a number of pins androds,

while the extensions 8 and 9 on each side of the front of the bracket 5serve as bearing plates for additional levers and members, as-will bepointed out. The top of theplate 5 has a pair of open- ,ings 24 atthe'rear and an additional pair 25 at the internal apparatus.

, each of the keys operate the contact springs and perform otheroperations will first be described in detail.

The lever key designated the Hold key is pivoted on the shaft 11 whichis journalled in ex tension plates 8 and 9. A spacer bushing is providedon the shaft '11 between each of .the keys 10, 20, and 30. The otherendof the key lever 10 is connected by pin 12 to the link member 13. Theend of the link member 13 is fork-shaped so that it moves in and out ona pin passed through the U-shaped member 15 which serves as a supportfora pair of insulated bushings 16. The U-shaped bushing support 15 isrotatable on a rod 14-fastened to the extension plate 8. Theconstruction just described is similar to that illustratedin connectionwith the lever key 30 shown'inl 'ig. 3, and it is seen that when thelever key 10 is moved downward and rotated about the shaft 11 it impartsmovement to the link member 13 by means of pin 12. Link member 13engages the pin in the U-shaped member 15, forcing the member outwardso. that the bushings 16 will engage the armature spring 80 and force itto make contact with its make spring. The lever key 10 operatesindependently of any of the other lever keys and it is likewise U-shapedbushing support 33., The support 33 in turn is pivoted on the bottom ofthe extension plates 8 and- 9 by. the rod 34, asis shown in Fig. 3. Aninsulated bushing 23 is rigidly secured ,on the top side of the linkmember 22 so that itcan engage and operate the armature sprlng.82 whenthe handle of the key lever 20is depressed. This action likewise movesthe rod 35 outward, thereby moving the bushing, support 33 so that bushing 38 on the left of the support 33' engages armature spring 81 and thebushings 36 and '37 on the right-hand side of the'support 33 can engagearmature springs 83 and 84 to operate them. The operation of lever key20, therefore, moves the bushings 23, 38, 3'7, and 36 at the same timeto engage. their associated armature springs.

The lever key 30, termed the Out key, is pivoted on the shaftlll and theopposite end is pivoted by pin 31 to the link member 32. The

- other end of link member .32 is fork-shaped so as to engage the rod35. This arrangement of lever -key is clearly shown in Big. 3. The op--eration of lever key 30 rotates the link member 32 about pivot 31 andforces the -fork shaped end into engagement with rod which is secured tothe bushing support 33. The bottom of this bushing support 33 is pivotedbetweenthe frame members 8 and sby the pin34 and it is seen that whenthe lever, key 30 is operated or moveddownward the bushing support-331srocked about the pivot 34 by the linkmember 32,i.t hereoutward from thefork-shaped end of link 22 by link member 32, and for this reason leverkey 20 operates all four bushings, while the lever key 30 will onlyoperate bushings 36, 3'1, and 38. When key 30,1 'ig. 3, for example, isoperated, the arrangement is such that the key is held in its operatedposition until it is released. This is brought about" by thetoggleoper-- ation which takesplace when pin 31 connecting .the ends ofkey '30 and link 32 is moved upward and it in turn rotates bushingsupport 33 about shaft 34. The pin 31', therefore, assumes a positionbeyond a center line drawn between the shafts l1 and 34 to hold the keyin its operated position. A stop rod 66 secured in the mounting plates 8and 9 serves as a stop for the normal position, of the keys.-

A locking member 40 is securely held and pivoted by screw 41 to thebottom surface of mounting plate 5. This locking member has a pair ofwing-shaped surfaces 42 and 43, the wing 42 adapted to be engaged by thefork-shaped end of link member 32 when it is operated, while the wing 43is adaptedito be engaged by the fork-shapedy end of link member 22. Thislocking member 40 is for the purpose of preventing the operation ofeither lever key 20 or ;30 when either one of them has already beenoperated. For example. should key 20 be operated;

prevented from being moved'because of the op-;

erated condition of key 20. It is therefore seen thatonly one of thekeys 20 .or30 can be operated at a time.

The lever keys 10, 20, and 30 after having once been operated maybeeither manually or automatically restored to their normal position. Ac-

cording to the invention, novel automatic means is provided forreturning the keys to their normal positions which is controlled by theremoval and replacement of the handset on the cradle member. Referringto Fig. 1, it will be seen that the handset is shown removed from thecradle member 1,'thereby permitting the-plunger 45 which controls theswitchhook springs SW, Fig. 5, to be operated. When plunger 45 isreleased, it permits the rod- 50, to which it is attached, to movevertically with it, as shown in Fig. 3. Although in 1 the handset hasbeen s own removed from the cradle member 1, in 3 the cradle member isshown with the handset upon it, so that the pin 50 bears upon theinsulating washer 54 which is attachedto themovabl'e lever arm 52.- Thelever arm 52 is pivoted so that it is rotatable-about the pivot pin'53which is secured in the extension plates 6 and 7. A pair of. like-shapedflat lever arms 56 are secured tog'ether as a unit by means ofthe pins55; 61,

' bears down upon the lever,52, which is thereby turned about its pivot53 and at 54 engagesthe pin 55 to give a slight upward movementv to thelever 56. A link member 60'is pivoted by pin 61 to the lever 56 and theopposite end is securely pivoted to the bearing pin 62 which isjournalled in the extension plates 6 and 7,. The end of the '5 linkmember 60 is provided with a rod 71 extending from each side of the linkmember 60 and the ends are provided with insulated bushings 70 and '72.With this arrangement it is seen that when lever 52 is moved downwardl-it moves lever 56 upward by the hook 54 engaging the pin 55. Thisimparts a rotary motion to the link member 60 because it is pivoted bythe pin 61 and this moves the linkmeinber 60 about its pivot 62, so thata forward thrust is 15. imparted to the plate 56. The pin '71 therebymoves the bushings '10 and 72 downward so that they bear against thelocking springs '73 and 75, as seen in Fig. 2.

The forward ends of. the lever 56 are riveted together by the pivotmember 63' to a release arm ,64. This release arm, as shown in Fig. 3,is rotatable about theshaft 34, so that forward movement of the. lever56 will pivot the arm ,64

about the, pin 34 and rivet 63 and the releasing 5 rod 65 which issecurely fastened to the arm 64 willthereby exert pressure upon the topside of each of the link members 13, 22, and 32 of the respective keys10, 20, and 30. This down-' ward motion of the release rod 65 restoresthe keys totheir normal position againstthenormal stop rod 66. Therelease rod. 65 is limited in its movement by the crescent-shaped slot65 cut in the'mounting plate 8 in whichit rides; The restoring action ofthe lever keys is as- 35 sisted materially by the spring tension stored5 is moved longitudinally rearward due to the tension stored in thelocking springs 75 and 73 which bear against the bushings 70 and 72 andimpart a rotary motion to the link member 'about its pivot 62. Thismotion is transmitted through the pivot'pin 61 to the lever 56. 5

. The locking springs '73 and '75 are each providd at their extremitieswith projections '14 and 76, respectively, which are formed out of themetal of which the locking springs are made. These projections extendupward into the path of movement of the armature springs 83 and'82,

so that, for example, when the'bushing- 37 engages armature spring .83to move it, the edge of armature spring 82L slides over the top of theproject-ion '74 and the spring is locked in its opcrated'position,although the bushing 3'7 has been restored. The same action takes placewhen armature spring 82 is operated by bushing 23 and it is locked, bythe projection 76 of lockiiig spring 75, and the armature spring remainsin this position although thebushing 23 may be restored to ,normalf Inthe normal, positionof the key unit the pin 50 bearson the lever 52 dueto the weight of the handset, and the lever *56 is given a longitudinalmovement about the pivot 62. The link member 60 thereby moves the rod'71- supporting bushings 70'and 72 upon their respective lockingspringsand '73, so that normally the locking projections 74 and 76 areout of thepath of" 5 movement of the armature springs 32 and 83.

However, as soon as the handset is removed from the cradle member,motion is imparted, as has been pointed out,'to the lever 56 and,zdue tothe tension stored in the locking springs 73 and 75, link member 60 isgiven a partial rotation about its pivot point 62 which in turn istransmitted to the lever 56 by way of the pin 61. Projections 74 and 76are thereby. placed inoperative relation to the armature springs -82 and83, and the replacement of the handset on the cradle member and theconsequent movement of the lever 56 will turn the link member 60 aboutits pivot 62 and move the bushings-'70 and '72 against locking springs73 and 75 to disengage the projections '74 and 76.from armature springs82 and 83. In addition to serving as locking springs for armaturesprings 82 and 83, the springs. '74 and. 76 likewise control contactsprings 78 and 79.

Referring now more particularly to Fig. 5, this shows. a schematicdiagram of the circuit ar-' rangement involved with a diagrammaticrepresentation of the key unit of the invention. The telephone circuitis of the usual type and in-- cludes a transmitter T, a receiver R, anda calling device 18 which has a set. of impulse springs connected intheline circuit and a set of shunt springs for short circuiting'thetransmitter and" receiver whenthe calling device 18 is operated. Aninductance coil'I-N is also provided, as are the switchhook contacts SWwhich are controlled directly by the switchhook operating button 45controlled by the handset. The local .line circuit L1 and L2 is providedwith the ringer RG and these conductors extend to the switchingapparatus located in the local exchange. In answering or making a localcallit is not necessary to operate any of the keys. 10, 20, and 30, asthe line conductors L1 and L2 normally extend over a circuit path fromthe line L1, normally closed contacts and armature.

springs 81, a push-button contact '19, throughmatic telephone system toprovide communication, for example, between a number of telephone;situated in close proximity to each other,

such as inthe same building, and co ections means of the calling device18. A number of L3 and Lei-extend to other automaticswitchin'g apparatusand by means of the lever keys 1 0,

20,and 30 control the establishment of connctions, either incoming oroutgoing over one or moreltrunk lines leading to a public exchangetelephone system, which. may be either of the automatic or manual type;i

In briefly describing the operation of the varicus circuitchangesbrought about bythe operation of the keys, it may first bepointed out that each telephone is provided with a ringer such as RG forinforming the ociated subscriber of" of operating any of the lever For amore detailed explanation of the circuit 1 are established throughautomatic swi hes by 1 other conductors including the'line conductorsthe presence of an incoming local call. 'Howwith keys are to be placed,eitherall of the teleph es may be provided with a sub-base 3 and acorresponding number of lever keys 10, 20, and

5 30, or only a certain number of them may be so provided for all thetrunks extending to the main exchange. This one signal is placed in sucha position that it will be visible or audible toall of the telephonesubstations in the local exchange, so that a person equipped with atelephone provided with a sub-base and keys may answer any of the callsby operating the proper key. It will be noted in Fig. 5 that the key setunit is indicated only diagrammatically with the keys in their normalpositions and ma similar position or rear view as indicated in Fig. 4 ofthe drawings.

When an incoming call from the public exchange is received over one ofthe trunk lines and the trunk signal is operated in a manner so that itis noted by a person having one of the telephones equiped with asub-base and the keys, he will answer the call by first removing the.handset from the cradle 1. Removing the handset permits the plunger tomove upward and operate the switching springs SW to close the linecircuit. The plunger 45 permits the rod to move upward and allow thelever 52 to move about its pivot 53. This action permits the lever 56to-move forward and rotates link about ,the pivot 62 so that thebushings and 72 will .be forced upward by the tension stored in thelocking springs 73 and 75, thereby permitting the contact springs 78 and79 controlled by these look-- ing springs to be operated. The tensionstored in the locking springs 73 and furnishes the motive power formoving the plate 56 backward.

After the handset is removed, the key, 20 is then moved downward and,according to the ar' rangement, link member 22 will move its bushing 23into engagement with armature spring 82 and, due'to the fork-shaped endof link mem ber 22 engaging the lever the, bushing sup port 33 islikewisemoved an cih gdingly, bushings 36, 37, and 38 are forced intengagement with armature springs 84, 83, and 82, respectively. As soonas armature spring 82 closes its make contact through the 'action ofbushing 23 moving the spring to the left, the projection 76 on thelocking spring 75 engages with the edge oi!v this armature spring, sothat it remains'operated eventhough the bushing 23 is subsequentlydisengaged from armature spring 82. A, similar action takes place inconnection. with armature spring 83' which is moved by bushing 37 beyondthe edge of projection 74 of locking spring 73, so that the projection74 will hold armature spring 83 in its operated engagement with its makecontact even though the bushing 37 may subsequently be disengaged fromthe end of the armature spring 83;

The above operations disconnect the local line circuit comprising theline conductors L1 and L2 from the telephone circuit ,at the normallyclosed contacts of armature springs 81 and 84, and com nects it insteaddirectly by way of these armature springs and their normally opencontacts to. the trunk line conductors L3 and L4. The contact springs 79 are opened, while contact springs 78 are closed so as to performcertain operations the t 1,956,880 ever, in a system in whichtelephones. provided local exchange'apparatus for connecting thesubscribers telephone with the trunk line over which the call is beingmade. The closing of armature spring 83 on its make contact is withouteffect at this time. The closing of armature spring 82 on its makecontact completes a circuit to the local exchange apparatus foroperating certain relays for a purpose pointed out in theabove-mentioned co-pending application. If the incoming call is for thesubscriber who has answered, he proceeds with the conversation. However,if the callis for another person at another of the telephones, it

may be transferred by manually restoring the answering keyv 20. ,Thisaction retracts the insu- -lated bushing 23 from armature spring 82, butthe armature spring does notdisengage from its normally open contactbecause it is locked in its operated position by the extension 76 onlooking spring 75. The bushing support 33 is likewise permitted torestore to normal, which restoring motion is assisted by the'tensionstored in the operated armature springs 81 and 84. Armature spring 83,however, is now locked operated to-its normally open contact by theprojection 74 on looking spring 73. Armature springs 81 and 84,therefore, restore their operating contacts to their normal positions.The subscriber then operates his calling device 18 to set up aconnection toth'e other subscriber to whom the incoming trunk call is tobe transferred, and'when he responds he is requested to operate hisansweringtrunk key,whereupon the call is automatically transferredthrough suitable circuit arrangements'to the trunk upon which theincoming call is made. As soon as the subscriber making the transferreceives atone to indicate that the other subscriber has picked up thetransferred call, he replaces his handset upon the cradle 1, therebydepressing the hookswitch operating member 45 and this in tum-operatingthe rod 50 downward. The lever 52 thereby moves the lever 56 forward bymeans of the hook 54 and rotates the link 60 about its pivot 62.Bushings 70 and 72 are thereby given a slight rotary downward motion adistance sufficient to move the locking springs 73 and 75 downward sothat the projections 74 and 76 will disengage from armature springs 82and'83 and permit them to restore and open their associated normallyopen contacts.

-Contacts 78 and 79 are likewise restored by the rear'of the key setthrough the tension stored in the-locking springs 73 and'75. This actionmoves the release arm 64 about its pivot points 34 and 63 and permitsthe release rod 65 to move out of the path of movement of the lever keysand their associated link members. The telephone user then operates theOut key 30, which, through the medium of the link member 32, moves thebushing support 33 about its pivot 34, as is clearly shown in Fig. 3,forcing the bushings 36, 37, and 38 into engagement with armaturesprings 81, 83, and 84 and operating their associated contacts. Theoperation of the key 30, it will be noted, only moves the bushings36,37, and '38, and the" bushing 23 pulses generated ting up thisconnection,

of locking spring 73 by closed, due to the release the bushing 70, andcomplete circuits for performkey 30 be attempted to will prevent such 50ing certain switching operations and to prevent intrusion on this trunkline by any other telephone: while'this trunk is inuse; The contactsprings 79 are at this time opened, but without eifect.

When the subscriber has completed the conversation and desires todisconnect, he merely restores the handset upon the cradle member 1,thereby depressing the switchhook operating member and moving the roddownward onto the lever 52 to move the lever 56 forward and pivot thelink member 60'about the pivot point 62. This permits bushings and 72 tobear'onto locking springs 73 and 75 and disengage the projection '14 83and permits it to from the armature sp'ringfurther result of the restoreto normal. As a movement of the lever-56, the release arm 64 has arotary motion imparted to it about its pivot 34 so that it moves thereleasing rod 65 against the end of the key lever 30 at the pointapproximately opposite the pivot point 31 and initiates the releaseaction of the key which is accelerated by the tensionstored in thearmature springs 81. 83, and 84,-until the key 30 strikes the stop rod66, whereupon all of the armature springs disengage from their operatedcontact springs and permit the apparatus at the central oflice and atthe local ofllce to restore to its normal condition preparatory toreceiving additional incoming or outgoing cal-la;

If at any time during the existence of either an incoming or an outgoingcall the corresponding key should be operated, it will be impossible forthe user of the telephone to operate the other key because of theinterlocking arrangement.

key 20 be operated, the

For example, should the locking plate 40 will-be moved by the action ofthe link member 22 engaging the wing 43 and rotating the member 40aboutits pivot 41 so that the wing 42 will be resting against theforkshaped end of link 32. Irrthis event, should the be operated, thewing 42 action, as the pressure exerted against wing 42 will exertacorresponding pres sure against wing 43 which-presses against the endof link member 32. Howeyer, thiswill'nott result in the release orrestoration of the key2il because this key, together with the linkmember 22, is in its operated position and, therefore, due to the togglearrangement, is beyond the line 'center between the two pivot points 21and 34.

If at anytime. a connection with the public exchange is desired to betransferred from the answering or the calling telephone to anothertelephone in the system, either the key 20 or the key 30 is restoredmanually to normal position, thereby completing a holding circuitextending over the trunk line L3, armature spring 83 which is lockedclosed .by the projection '74 on the looking spring '73, closed contacts'79, normally closed contacts of armature spring 81 and out over lineL4. This short circuit across the'line conductors L3 andv L4 preventsthe automatic switches at the public exchange or central offlce fromreleasing the connection with this subscriber. The subscriber dials thenumber of the party to whom he'desires to transfer the call and thisparty in turn operates his answering key, whereupon the first party mayreplace his hand! set upon a portion of the connection.

A' push-button grammatically in Fig. 5 is connected through suitablecontacts in one side of the line circuit L1, and the purpose of thisisthat if the trunk line to the public exchange is connected to a manualexchange instead of an automatic exchange, the person or user of-thetelephone may flash the operator, whereas ordinarily he would move thevhookswitch member 45 up and down slowly to 19 shown infF'ig. 1 and alsodia-- switchhook member and release flash the lamp before the operator.However. in

the instant case the operation of switchhook member 45 wouldautomatically release all of the keysand knock down the connection and,there-.

fore, the key 19 is provided. This key is also used when making calls ifthe user of the telephone should inadvertently make a mistake whenoperating the calling :device' 18. j in this'case may be released byoperatingthe push-button 19 without operating the switchhook member 45.

In case a larger number of exchange trunk lines are to be madeaccessible to any of the telephones, an additional key such as key 10-is provided. This key 10, upon being operated, merely moves the linkmember 13 to engage bushing 16 with armature spring-80 and close itscontacts. This key is restored to normal by the release bar 65 when thehandset is replaced upon the switchhook member. This key, it will benoted, has no looking or interacting motion with either the answeringkey 20 or the out key 30. It merely closes the armature spring 89 uponits make contacts and when released 'opens these contacts.

The connection either held by the user'ofthe telephone or is Itransferred to another telephone in the system and then a 'second callcomes in, over another trunk line, the key 10 may be operated. In thiscase the second trunk call may be transferred to the desired other partyor held while the first trunk call is taken care of. When the secondtrunk call is being held, the user of the telephone may re n to it" atany time either before or afterthe rst trunk call is disposed of.Thearmature spring 80, upon closing, onto its make contact, completescircuit connections at the 10- cal exchange which operates the mechanismto take care of situations of this nature. I

What is claimed is:

lfIn a telephoneinstrument, a plurality of sets of contact springs, apair of keys for operto the operation of one of said keys for operating;all of said contact springs, means responsive to the operation of theother of said keys for operating only certain of said sets of contactsprings,

means for holding said keys in their operated position, and means forreleasing said keys to restore all of the contact spring sets to theirnormal positions. v

2. In a telephone instrument, a plurality of sets of contact springs, aplurality of keys for operating said'contact springs, means for lookingsaid keys in their operated position, means responsive to the operationof one of said keys for operating all of said contact springs, meansating and releasing said springs, means responsive I for operating allof said sets of contact springs,

a second key for operating only certain of said sets of contact springs,means responsive to the operation of either key for locking it in itsoperated position, and means responsive to the operation of either oneof said keys and controlled by said locking means for ation of the otherkey.

';5. In a telephone instrument, a plurality of sets of contact springs,a first key for operating all of said sets of contact springs, a secondkey preventing the operfor operating only certain ones of said sets ofcontact springs, means for locking said 'keys in their operatedposition, means responsive to the operation of either of said'keys foroperating said locking means and preventing the operation of the otherkey, and means for releasing said locking means for automaticallyrestoring said keys to their normal positions.

6. In a key set, a plurality of sets'of contact springs, a pair of keysfor operating said contact springs, means responsive to the operation ofone of said keys for operating certain of said sets of said contactsprings, means responsive to the operation of the other oi said keys foroperating all of said sets of contact springs, and means for lockingsaid operated sets of contact springsin' their operated positionsindependent .01 the position oi the keys.

7. In a key set, a plurality of sets of contact springs, a pair of keysfor controlling said springs, means responsive to the operation or oneof said keys for operating certain of said sets of contact springs,means responsive to the operation of the other oi said keys-toroperating all or said sets of contact springs, means for releasing saidoperated keys, means responsive to the operation of said sets or contactsprings for locking them in their operated position after said keys havebeen released, and means for releasing said sets of contact springsindependent of the release of said operatedkeys. Y

8. In a telephone instrument, a plurality of sets of contact springs,keys for operating said contact spring sets, each of said keys operatingsaid contact spring sets in difierent combinations, said keys manuallyrestored at will, means responsive to the operation of saidcontact'springs for locking them in their operated position independentof the position of their associated keys, and an operating memberautomatically controlled for unlocking said operated contact spring setsand for restoring any operated key to normal.

9. In an assembly, a plurality of sets of con-' tact springs, a keyhaving means for operating a particular set of said sets, to theexclusion of the other oi. said sets, a second key having means foroperating a plurality of said sets excluding the set operable by saidfirst key, and a third key having means for operating a set of said setsnot operable by either the first or second key and including mechanismfor also operating the means operable by the second key wherebyoperation of the third key also effects the operation of.the setsoperable separately by the second key. i

10. In an assembly, a plurality of sets of con tact springs, keys foroperating said sets of contact springs; means responsive to theoperation of certain springs of said sets Iorlocking them in theiroperated position independent of the subsequent operation of theiroperating ,keys, while other springs of said sets not equipped withlocking means are permitted to follow the movements of said keys; andamember, operable at will, arranged to automatically release any of thespring sets which have been locked and to at the same time eiiect therestoration of any actuated ones or said keys.

I HERBERT F. OBERGFEIL.

